Automobiles have air conditioners for reducing the temperature of air in an automobile passenger compartment. The air conditioner operates by compressing refrigerant using a compressor, reducing the temperature of the compressed refrigerant, and then expanding (uncompressing) the refrigerant to reduce the refrigerant temperature. The expanded refrigerant then flows through an evaporator used to lower the temperature of the air in the passenger compartment. Variable displacement compressors vary compressor displacement to vary the flow rate of refrigerant through the compressor. After the compressor establishes a sufficient pressure difference in the air conditioner, it may be advantageous to reduce the displacement or capacity of the compressor and operate at low refrigerant flow rates. Under low flow conditions, suction reed flutter in the compressor can create pressure pulsations that propagate into the air conditioner evaporator. These pressure pulsations may be heard inside the vehicle passenger compartment.
It is known to include a suction shutoff valve (SSV) in a compressor to restrict communication of the suction reed flutter noise to the evaporator. However, a SSV providing adequate restriction at low flow conditions has undesirable flow restriction and pressure loss at high flow rates. At high flow rates it is advantageous to minimize the restriction of refrigerant flow to the compressor so the compressor can operate at maximum efficiency. What is needed is a SSV that has adequate restriction at low refrigerant flow rates and lower restriction at high refrigerant flow rates.